Contact wheel for abrasive belts



Sept. 19, 1961 s. JOHNSON CONTACT WHEEL FOR ABRASIVE BELTS Filed April 11, 1955 Haj INVENTORS 3774/1 16? A. JCV-M fO/V WJ Qua/b &/(M

United States Patent 3,000,149 CONTACT WHEEL FOR ABRASIVE BELTS Stanley L. Johnson, St. Paul, Minn., assignor to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Apr. 11, 1955, Ser. No. 500,593 6 Claims. (Cl. 51141) The present invention relates to grinding and abrading apparatus, especially adapted for use with coated abrasive belts or the like. More particularly, it pertains to novel contact or back-up wheels employed in such apparatus for supporting the abrasive belt running over said Wheels against the workpiece.

It has been known that the provision of grooves or indentations in the peripheral belt-contacting surface or rim of abrasive contact wheels tends to increase the aggressiveness or rate of cut of the abrasive belt running over the surface of such contact wheel. The increase in belt aggressiveness obtained through the use of such a wheel is attributed at least partially to the decrease in belt supporting area on the contact wheel with consequent increase in the unit abrasive pressure exerted against the workpiece. These surface irregularities have heretofore generally taken the form of parallel linear grooves and lands extending more or less across the surface of the rim. Maximum groove width and minimum land width obviously provides maximum unit pressure at the abrasive surface. However, the permissible width of the grooves or indentations is limited. Excessive groove width between adjacent lands on the surface of the contact wheel causes the belt to chatter against the workpiece thus resulting in uneven abrasion of the abraded surface.

In an effort to further increase the aggressiveness of abrasive belts, by further decreasing the belt supporting area without the disadvantages which accompany wide grooves, contact wheels have been employed having surfaces provided with series of parallel grooves of equal width and distance apart which extend angularly across the surface of the wheel identically in both directions. Grooves of one series cross those of the other so as to define many protruding belt-engaging lands which take the form of congruent rhombuses. Such contact wheels increase the aggressiveness of abrasive belts markedly over that of those in which the grooves extend in only one direction.

However, it has been found that when contact wheels are employed which have series of identically formed and positioned parallel grooves extending angularly across the surface of the wheel in both directions, slight but undesirable visible imperfections are left on the abraded surface of the workpiece. The imperfections are seen even after the workpiece has been subjected to plating operations. These visible imperfections result regardless of the material of which the surface of the contact wheel, over which the abrasive belt runs, is constructed. Thus, such prior art contact wheels are unsuitable in operations where accurately and uniformly ground surfaces are required. As a result, such wheels have never seen extended industrial use.

It is therefore an object of the present invention to provide an abrading apparatus wherein extremely high rates of cut are obtained from the coated abrasive material employed and yet which provide a visibly uniform abraded surface on the workpiece.

Other objects and advantages which are attained by the present invention will be apparent upon reference to the following description or will be specifically hereinafter pointed out. In the accompanying drawings:

FIGURE 1 is a front elevation of an abrasive contact ice wheel having a surface which is illustrative of the present invention;

FIGURE 2 is a section view of the contact wheel of FIGURE 1 taken along the line 2-2; and

FIGURE 3 is a representation of a portion of the peripheral surface of the contact wheel of FIGURE 1 shown as a planar expansion. v

Referring now to the accompanying drawings wherein like characters of reference denote corresponding parts, the abrasive contact wheel as shown in FIGURES 1 and 2 has a wheel body 11 provided with a central hole 10 for mounting the wheel on an arbor, and a peripheral surface 12 for supporting an abrasive belt running over the wheel against which the workpiece is held. The peripheral surface has provided therein a first series of parallel linear equidistantly spaced grooves 13 extending angularly across the surface and a second series of parallel linear equidistantly spaced grooves 14 extending across the surface of the rim across grooves 13 of the first series. Grooves 13 of the first series likewise intersect and cross grooves 14 of the second series. A plurality of congruently shaped protruding belt-engaging lands 15 are defined by the two series of grooves.

The circumferential distance between a point on one of the bounding surfaces of a groove of one of the series and the analogous point on the next adjacent parallel groove is defined as the circumferential pitch of the series. The circumferential pitches of the respective series of grooves of the depicted contact wheel are shown as P and P in FIGURE 3. I have found that in abrading operations where a contact wheel is employed wherein the circumferential pitch of one of the series of parallel grooves differs from that of the other series, no visible imperfections are produced on the workpiece surface. I know of no other abrasive contact wheels wherein the belt supporting area may be decreased (so as to increase unit abrasive pressure exerted against the workpiece) by provision of crossing grooves in the peripheral surface thereof which will also provide visually uniform abraded surfaces.

Thus by employing the abrasive contact wheels hereof, workpieces having completely visually uniform abraded surfaces, are finished in a fraction of the time necessitated by the use of heretofore known contact wheels. As a result, in operations where a visually uniform abraded surface is essential, such as the finishing of automobile bumper blanks which are thereafter electro-chemically plated, my contact wheels have made possible economy of operation heretofore unattained.

Three variables are to be considered in designing an abrasive contact wheel surface embodying the principle of this invention. These are groove width, perpendicular distance between grooves or width of land, and groove angle or the angle between the direction of the groove and the circumferential direction. The desired difference in circumferential pitch of the two series of grooves may be obtained by employing different values for a single variable, or for any two variables or for all three variables.

For example, it will be seen upon reference to FIGURE 3 that the groove widths W and W of the two series of parallel linear grooves are equal and the angles A and A which the grooves of the two series form with respect to the circumferential direction are also equal. However, the perpendicular distance between the grooves of the first series D exceeds that of the second series D Thus the respective circumferential pitches of the two series differ. Likewise, where the groove widths and the perpendicular distance between grooves of the respective series in a wheel are the same while the angles which grooves of the respective series form with the circumferential direction difier, the circumferential pitches of the respective series difler. The same is true of a wheel wherein the perpendicular distance betwen grooves of the two series and'the angles formed thereby with the circumferential direction are equal while the respective groove widths difi'er. In each case the defined lands are all substantially mutually congruent and quadrangular. I

When it is desired to form the contact wheel hereof by employing different values for two or all of the abovementioned variables, the values chosen must be selected With care for it is possible to choose certain combinations thereof wherein the resulting pitches will be equal. This undesirable eventuality may be discovered and corrected prior to the actual fabrication of the contact wheel by drawing out on a plane surface the planar expansion of thecontemplated surface, such as is shown in FIGURE 3, and measuring the pitches of the respective series.

The angles which the grooves of the respective series form with a circumferential direction should be such that no grooves extend circumferentially of the wheel, thus preventing any portion of abrasive belt surface from being continuously unsupported. Where the angles formed by grooves of one or both of the respective series are within the range of from about 7590 degrees, the contact wheel becomes increasingly noisy in operation. I prefer to form my contact wheel such that grooves of both series extend across the surface of the wheel at angles within the range of from about 45-7 5 degrees.

Although the grooves of a series which extend across the peripheral surface of our novel contact wheel are parallel, they need not necessarily be linear but may alternatively be slightly curvilinear.

The contact wheel hereof may be formed in the manner and of those materials well known to those skilled in the art. For example, the grooves may be cut into the surface of the wheel after the fabrication thereof or they may be molded integrally with the surface at the time of fabrication. Or the desired surface pattern may be formed by atfixing adherently to the surface of the wheel in the desired pattern individual preformed blocks which serve as the belt-engaging lands. The wheels may be of a single material throughout, such as metal or rubber, or be formed from combinations of such materials. An example of the last-mentioned type is a wheel comprised of a metal hub on which is molded a rim of resilient plastic or rubbery material, the latter having the novel surface described herein.

I claim:

1. A contact wheel for. an abrasive belt and the like which renders said belt highly aggressive while permitting said belt to effect a visually uniform abraded surface on the work piece, characterized in that the peripheral surface of said wheel is provided with a first series of equidistantly spaced parallel grooves of equal width of which each groove extends across the peripheral face of said wheel, a second series of equidistantly spaced parallel grooves of equal width similarly extending across the peripheral face of. said Wheel such that grooves of said second series intersect and cross grooves of said first series and grooves of said first series intersect and cross grooves of said second series, the grooves of said first series having a circumferential pitch differing from that of the grooves of said second series, said crossing grooves defining a plurality of substantially congruent protruding quadrangular 1y shaped belt-engaging lands.

2. A contact wheel for an abrasive belt and the like which renders said belt highly aggressive while permitting said belt to effect a visually uniform abraded surface on the workpiece, comprising a mounting hub and a resilient rim securely attached to said hub, the peripheral surface of Said rim being provided with a first series of equidistantly. spaced parallel grooves of equal Width of which each groove extends across the peripheral face of said wheel, a second series of equidistantly spaced parallel grooves of equal width similarly extending across the peripheral face of said Wheel such that'grooves of said second series intersect and cross grooves of said first series and grooves of said first series intersect'and cross grooves 4 of said second series, the grooves of said first series having a circumferential pitch differing from that of the grooves of said second series, said crossing grooves defining a plurality of substantially congruent protruding quadrangularly shaped belt-engaging lands.

3. A contact wheel for an abrasive belt and the like which renders said belt highly aggressive While permitting said belt to effect a visually uniform abraded surface on the workpiece, comprising a mounting hub and a unitary resilient rim of uniform composition securely attached to said hub, the peripheral surface of said rim being provided with a first series of equidistantly spaced parallel grooves of equal width extending across the peripheral face of said wheel, a second, series of equidistantly spaced parallel grooves of equal width similarly extending across the peripheral face of said wheel such that grooves of said second series intersect and cross grooves of said first series and grooves of said first series intersect and cross grooves of said second series, the grooves of said first series having a circumferential pitch differing from that of the grooves of said second series, said crossing grooves defining a plurality of substantially congruent protruding quadrangularly shaped belt-engaging lands.

4. A contact wheel for an abrasive belt and the like which renders said belt highly aggressive While permitting said belt to effect a visually uniform abraded surface on the workpiece, comprising a mounting hub and a unitary resilient rim of uniform composition securely attached to said hub, the peripheral surface of said hub being provided. with a first series of equidistantly spaced parallel linear grooves of equal width extending across the peripheral face of said wheel, a second series of equidistantly spaced parallel linear equi-width grooves of greater width than said first series, the grooves of said second series similarly extending across the peripheral face of said wheel at an angle with respect to said circumferential direction identical with that of said first series such that grooves of said second series intersect and cross grooves of said first series and grooves of said first series intersect and cross grooves of said second series, the perpendicular distance between grooves of said first series being equal to the distance between grooves of said second series, said crossing grooves defining many substantially congruent protruding quadrangularly shaped belt engaging lands.

5. A contact wheel for an abrasive belt and the like which renders said belt highly aggressive while permitting said belt to effect a visually uniform abraded surface on the workpiece, comprising a mounting hub and a unitary resilient rim of uniform composition securely attached to said hub, the peripheral surface of said hub being provided with a first series of equidistantly spaced parallel linear grooves of equal Width extending across the peripheral face of said wheel, a second series of equidistantly spaced parallel linear grooves of a width equal to that of said first series, the grooves of said second series extending similarly across the peripheral face of said Wheel at an angle with respect to said circumferential direction identical with that of said first series such that grooves of said second series intersect and cross grooves of said first series and grooves of said first series intersect and cross grooves of said second series, the perpendicular distance between grooves of said first series being greater than the perpendicular distance between grooves of said second series, said crossing grooves defining many substantially congruent protruding quadrangularly shaped belt engaging lands,

6. In a contact Wheel for driving and cushioning an abrasive belt, an elastic tire having a longitudinal axis of rotation and providing a generally cylindrical peripheral surface, said surface having a plurality of substantially parallel main serrations equally spaced fully thereo-ver and extending diagonally to said axis of rotation to define a plurality of separate ribs, said ribs being divided by a plurality of substantially parallel cross-serrations equally spaced fully thereacross and intersecting said main serrations to define a pluralityof closely adjacent islands, said cross-serrations peing substantially narrower than said main serrations and each extending transversely continuously across said surface, said main serrations having a circumferential pitch difiering from that of said cross serrations whereby said islands are disposed in staggered arrangement.

References Cited in the file of this patent UNITED STATES PATENTS 

